Combined hydrotreating and process

ABSTRACT

First ( 210 ) and second ( 240 ) feedstocks are hydrotreated in an integrated hydrogenation plant ( 200 ) using a hot separator ( 230 ) that provides a vapor stream containing at least some of the hydrotreated first feedstock ( 210 ), wherein the second feedstock ( 240 ) is mixed with the vapor stream at a position downstream of the separator ( 240 ) and upstream of the a second hydrotreating ( 250 ) reactor to form a mixed second feedstock that is fed into the second hydrotreating reactor ( 250 ) to produce a ultra-low sulfur product.

FIELD OF THE INVENTION

The field of the invention is petrochemistry, and particularlyhydrotreating of diesel and fluid catalytic cracking gas oil feedstocks.

BACKGROUND OF THE INVENTION

Hydrotreating is a commonly used process in many modern refineries, inwhich hydrogen is contacted in the presence of a catalyst with ahydrocarbonaceous feedstock to remove impurities, including oxygen,nitrogen, sulfur, and unsaturated hydrocarbons. Consequently,hydrotreating is frequently employed to reduce the sulfur content fromrefined intermediates and is also commonly referred to ashydrodesulfurization. Hydrodesulfurization is typically used within arefinery in combination with processes including feed pretreatment ofcatalytic reformers, catalytic crackers, and hydrocrackers, productquality improvement for naphtha, diesel, jet, heating oil and residues,saturation of olefins, and polycyclic aromatics. There are numeroushydrotreating configurations and processes known in the art, andcontinuous efforts to reduce energy and material consumption led tointegration of hydrotreating reactors in various processes.

For example, in one integration concept, a hydrotreater is combined witha hydrocracker as disclosed in U.S. Pat. No. 3,328,290 to Hengstebeckthat describes a two-stage hydrocracking process wherein fresh feed iscombined with effluent from the hydrocracking stage and the combinedstreams are then introduced into a hydrotreating stage. A higher-boilingfraction is then separated from the hydrotreater effluent andfractionated to produce a light product and a heavier-bottoms stream,which is then recycled with hydrogen-containing gas back to thehydrocracking stage.

Another example U.S. Pat. No. 6,235,190 to Bertram describes anintegrated hydrotreating and hydrocracking process in which twohydrotreating catalysts of different activity are operated in series toprovide improved products that are then subjected to a hydrocrackingprocess to convert the hydrotreated effluent to lighter products with areduced aromatic hydrocarbon content.

In a further example, as described in U.S. Pat. No. 6,261,441 to Gentryet al., a combined hydrotreating/hydrocracking process is described inwhich a hydrocracking stage is followed by a hydrodewaxing stage with asingle feed and a bottoms fraction recycle to produce a naphtha product,a distillate boiling above the naphtha range, and a lubricant.

In yet another system, as described in U.S. Pat. No. 6,328,879 toKalnes, two independent feedstocks are hydrocracked in a catalytichydrocracking process that employs a hydrocracking zone, a hydrotreatingzone, and a high pressure product stripper to produce various productsfrom two feedstocks, wherein the products have a lower boiling pointrange than the feedatocks.

Alternatively, more than one hydrotreater reactor, and or catalyst bedsmay be employed for catalytic hydrogenation as described in U.S. Pat.No. 3,537,981 to Parker, or U.S. Pat. No. 6,103,105 to Cooper. WhileParker's process employs a first hydrotreating reactor coupled to aseparator that is in series with a second hydrotreating reactor, Cooperet al. employ two serially connected hydrotreating catalyst beds withoutthe use of a separator. However, both Coopers and Parkers configurationare typically limited to only a single feedstock. Alternatively, asdescribed in U.S. Pat. No. 5,958,218 to Hunter, two hydrocarbonfeedstocks are hydrotreated in parallel while hydrogen flows in seriesbetween the reactors. While Hunters configuration allows hydrotreatingof two at least somewhat different feedstocks, the catalytic reactorswill generally operate at different hydrogen partial pressures.Consequently, the balance of the feedstocks will have to be properlybalanced with the particular hydrogen partial pressures to yield thedesired products.

Thus, although many integrated processes have provided at least someadvantage over other known conligurations and methods, suchconfigurations and methods are frequently limited to processes involvinghydrocracking, or hydrotreating of a single boiling range (e.g.,naphtha, diesel, gasoil, resid) feedetock. Consequently, all or almostall of the known hydrotreating processes require separate plants wheremore than one feedstock is employed. Therefore, there is still a need toprovide improved configurations and methods for hydrotreating ofpetroleum products.

SUMMARY OF THE INVENTION

The present invention is directed to configurations and methods forhydrotreating plants, and especially for integrated hydrotreating plantsin which at least two feedstocks with different boiling point ranges(e.g., gas oil and diesel oil) are hydrogenated.

In one aspect of the inventive subject matter, contemplated plantsinclude a first hydrotreating reactor that receives a first feedstockand produces a hydrotreated first feedstock and further include a hotseparator that receives the hydrotreated first feedstock and produces ahot hydrotreated liquid and a hot hydrotreated vapor that contains atleast a portion of the hydrotreated first feedstock. At least a portionof the hot hydrotreated vapor is mixed with a second feedstock to form amixed second feedstock that is fed into a second hydrotreating reactorto form a product, wherein the second feedstock has a boiling pointrange that is lower than the first feedstock. This configuration isespecially applicable where the sulfur content of the product of thesecond hydrotreating reactor must be maintained at a very low level.

In a further contemplated aspect, a gas oil first feedstock and dieseloil second feedstock are considered especially advantageous, especiallywhere the charge rate of the first feedstock and the second feedstockhave a ratio of between about 1:1 to about 1:2. Where appropriate, firstand/or second hydrotreating reactors may further receive ahydrogen-containing stream, some or all of which may be recycled in theplant from an effluent of the second hydrotreating reactor or may be amakeup hydrogen stream. Furthermore, it is contemplated thatconfigurations according to the inventive subject matter may be realizedin a new plant. However, the hot separator and the second hydrotreatingreactor may also be integrated as an upgrade into an existinghydrotreating plant.

Consequently, a method of hydrotreating may comprise a step in which afirst feedstock is hydrotreated in a first hydrotreating reactor toproduce a hydrotreated first feedstock. In another step, thehydrotreated first feedstock is fed into a hot separator that produces ahot hydrotreated liquid and a hot hydrotreated vapor that contains atleast a portion of the hydrotreated first feedstock, and in yet anotherstep, at least a portion of the hot hydrotreated vapor is mixed with asecond feedstock to form a mixed second feedstock. In a still furtherstep, the mixed second feedstock is fed into a second hydrotreatingreactor to form a product.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a schematic view of an exemplary configuration of a prior arthydrotreating plant.

FIG. 2 is a schematic view of an exemplary configuration of ahydrotreating plant according to the inventive subject matter.

DETAILED DESCRIPTION

Various known configurations and processes for desulfuration and/ordenitrification using hydrotreating of a feedstock employ ahydrotreating reactor in which a hydrocarbonaceous feed is reacted withhydrogen in the presence of a catalyst to form H₂S and/or NH₃ fromsulfur- and/or nitrogen-containing compounds in the feed. Prior art FIG.1 depicts a typical configuration 100 for such plants. Here, a singlefeedstock (e.g., diesel) 110 is passed through a heater 120 andsubsequently fed into a hydrotreating reactor 130. Hydrogen (separately[via line 141], or in combination [via line 142] with the feedstock) isadded to the catalyst in the hydrotreating reactor and the hydrotreatedproduct 112 is (after a cooling step in cooler 180) separated inseparator 150 into a gaseous portion 112A, which predominantly compriseshydrogen and hydrogen sulfide, and a liquid portion 112B, whichcomprises hydrotreated gas oil, wild naphtha, and remaining sour gas.The hydrogen from the gaseous portion is typically purified in anabsorber 152 with an amine-containing solvent, and recycled (supra) intothe hydrogen reactor via compressor 160. The hydrotreated feed 112C canthen be retrieved from column 170 along with wild naphtha 112D and sourgas 112E. While such configurations work relatively well for a singletype of feedstock (e.g., gas oil, diesel, etc.), known plants withmultiple feedstocks (e.g., gas oil and diesel) generally requiremultiple and separate hydrotreating configurations, which addsignificant cost to construction and operation of such plants.

In their efforts to improve configurations and methods for hydrotreatinghydrocarbonaceous feeds, the inventors have discovered that multipletypes of feedstock (i.e., feedstocks with different boiling pointranges—e.g., gas oil and diesel) can be hydrotreated in an integratedconfiguration, in which a hot separator is fluidly couple( hydrotreatingreactor, and in which a single hydrogen recycling loop (e.g., comprisinga cooler or heat exchanger, a liquid/gas separator, an amine scrubber,and a compressor) can be employed for both hydrogen reactors.

Thus, in a particularly preferred aspect of the inventive subjectmatter, a plant comprises a first hydrotreating reactor that receives afirst feedstock and produces a hydrotreated first feedstock and a hotseparator that receives the hydrotreated first feedstock and produces ahot hydrotreated liquid and a hot hydrotreated vapor that contains atleast a portion of the hydrotreated first feedstock, wherein at least aportion of the hot hydrotreated vapor is mixed (preferably at a positiondownstream of the separator and upstream of the second hydrotreater)with a second feedstock to form a mixed second feedstock that is fedinto a second hydrotreating reactor to form a product, and wherein thesecond feedstock has a boiling point range that is lower than the firstfeedstock. In further contemplated aspects, the separator, the firsthydrotreating reactor, and the second hydrotreating reactor are operatedsuch that the product has a sulfur content of less than 100, morepreferably less than 50, and most preferably less than 15 ppm.

FIG. 2 depicts an exemplary configuration of a hydrotreating plant 200,in which two different hydrocarbonaceous feedstocks are hydrotreatedusing an integrated configuration with a single hydrogen recycle loop.Here, first feedstock 210 (e.g., gas oil ) is heat exchanged against thehydrotreated first feedstock 210′ and further heated in heater 202Abefore introduction into the first hydrotreating reactor 220. Thehydrotreated first feedstock 210′ is then fed into hot separator 230that is operated under conditions to separate hydrotreated firstfeedstock 210′ into hot hydrotreated liquid 210′L and hot hydrotreatedvapor 210′V, wherein the hot hydrotreated vapor 210′V contains at leasta portion of the hydrotreated first feedstock 210′. The hot hydrotreatedvapor 210′V is then mixed with the second feedstock 240 (e.g., dieselfeed) to form a mixed second feedstock 240′ that is fed (after heatexchange against product 260 and further heating in heater 202B) intothe second hydrotreating reactor 250. The second hydrotreating reactor250 produces product 260. A downstream separator 270 recovers at least aportion of the hydrogen from the product 260, and the recovered hydrogenis fed into a hydrogen recycle loop 280 (including cold separator 282and absorber 284) that eventually provides at least part of the hydrogenused in the first separator via compressor 290. Thus, it should berecognized that in contemplated configurations, the hot separator isoperated such that at least a portion of the feedstock is separated fromthe hydrotreated feedstock and fed into the hydrotreating reactor inwhich the second feedstock is hydrotreated.

It should be especially appreciated that the terms “hydrotreatingreactor” and “hydrocracking reactor” are not referring to the same typeof reactor. As used herein, the term “hydrotreating reactor” refers to areactor in which a hydrocarbon-containing feed is reacted with hydrogenin the presence of a catalyst under conditions that (a) result in lessthan 15% conversion, and more typically less than 10% conversion, and(b) result in the formation of H₂S and/or NH₃ from sulfur- andnitrogen-containing compounds in the hydrocarbon-containing feed. Incontrast, the term “hydrocracking reactor” as used herein refers to areactor in which a hydrocarbon-containing feed is converted to lighterproducts (i.e., the average molecular weight decreases), wherein theterm “conversion” or “converted” means that a particular percentage offresh feed changes to middle distillate, gasoline and lighter products(see e.g., “Hydrocracking Science And Technology” by J. Scherzer and A.J. Gruia; Marcel Decker, Inc.). Thus, contemplated hydrocrackingreactors will have a conversion of at least 15%, more typically at least30%, and most typically at least 50%.

As also used herein, the term “hot separator” refers to a separator thatis fluidly coupled to at least two hydrotreating reactors such that thehot separator receives an at least partially hydrotreated (or otherwiseat least partially purified) first feedstock at a temperature of about400° F. and higher, and wherein the hot separator produces a hothydrotreated vapor that (a) contains at least a portion of the firstfeedstock and (b) is feed into a second hydrotreating reactor.

With respect to the first and second feedstocks (210 and 240,respectively) it should be appreciated that various hydrocarbonaceousfeedstocks are considered suitable for use herein, and in especiallycontemplated aspects the first hydrocarbonaceous feedstock comprises gasoil and the second hydrocarbonaceous feedstock comprises diesel. In astill further especially contemplated aspect, the secondhydrocarbonaceous feedstock may also comprise cycle oil from an upstreamFCC (fluid catalytic cracking) reactor. However, in alternative aspects,suitable hydrocarbonaceous feedstocks also include crude or partiallypurified petroleum fractions, including light gas oil, heavy gas oil,straight run gas oil deasphalted oil, kerosene, jet fuel, etc.Furthermore, it is generally preferred that suitable first and secondhydrocarbonaceous feedstocks have different boiling point ranges,wherein the first hydrocarbonaceous feedstock typically has a boilingpoint range that is higher (at least 5 degrees centigrade, moretypically at least 10 degrees centigrade, and most typically at least 25degrees centigrade as measured from the initial boiling point in theboiling point range) than the second boiling point range.

Contemplated hot separators are preferably operated under conditionsthat will allow separation of the hydrotreated first feedstock into aliquid portion and a vapor portion, wherein the vapor portion comprisesat least a part of the hydrotreated first feedstock. Thus, it isgenerally preferred that contemplated hot separators will receivehydrotreated first feedstock that is not, or only partially cooled(e.g., by heat exchange with first feedstock). Consequently, it shouldbe appreciated that suitable operation temperatures for contemplated hotseparators are generally above 300° F., more typically above 400° F.,and most typically in a range between about 450° F. and 550° F.

Furthermore, it is contemplated that appropriate hot separators will beoperated at a pressure that is at or close to the pressure in the firsthydrotreating reactor and at a pressure that is at or above the pressureof the second hydrotreating reactor. Consequently, suitable hotseparators will typically be operated at between about 1000-2500 psi,and more typically at a pressure of about 1200 psi and about 2400 psi.However, where suitable it should be appreciated that the pressure mayalso be less than 1000 psi and especially contemplated lower pressuresare generally between 1000 to 400 psi, and even less. Similarly, wherehydrotreating conditions allow, hot separators may also be operated at apressure above 2500 psi, and suitable higher pressures include pressuresbetween 2500 to 4000 psi, and even higher.

With respect to the vapor comprising at least a portion of thehydrotreated first feedstock, it should be recognized the vapor willinclude significant quantities (i.e., at least 20 mol %, more typicallyat least 35 mol %) of hydrogen that has not reacted with components ofthe first feedstock in the first hydrotreating reactor. Furthermore, itis contemplated that the portion of the hydrotreated feedstock in thevapor may vary considerably, and will, among other parameters, typicallydepend on the quality of the first feedstock and the temperature andpressure conditions under which the hot separator is operated.

With respect to the composition of contemplated portions of thehydrotreated first feedstock in the vapor, it should be recognized thata particular composition of such portions will predominantly depend onthe particular composition and nature of the first feedstock. However,it is generally contemplated that preferred compositions contain atleast some material with a boiling point range that lies within theboiling point range of the second feedstock.

Dimensions and capacities of contemplated hydrotreating reactors willtypically depend at least in part on the particular feedstock, and theoverall throughput capacity of the hydrogenation plant. Thus, it iscontemplated that all known hydrotreating reactors are suitable for useherein. However, it is generally preferred that the hydrotreatingreactors will be operated under conditions that ensure hydrogenation ata relatively low level of hydrocracking (i.e., less than 15% conversion,more typically less than 10% conversion). Consequently, the nature ofthe catalyst may vary considerably. However, preferred hydrotreatingcatalysts will include those comprising cobalt, molybdenum and/or nickeldistributed on a carrier (e.g., alumina extrudate).

Furthermore, it should be recognized that by fluidly coupling the firsthydrotreating reactor to the second hydrotreating reactor via the hotseparator, the second reactor may be operating at a significantly higherpressure than a traditional standalone unit, which in turn will furtherreduce the amount of required catalyst for hydrotreating the secondfeed. It should be especially recognized that in preferred aspects ofthe inventive subject matter both hydrotreating reactors are operatedunder conditions effective to reduce the concentration of sulfur- and/ornitrogen-containing compounds in both feedstocks. Consequently, itshould be recognized that in preferred configurations both feedstocksare substantially not (i.e., less than 10%, more typically less than 8%)converted to lower boiling point products. In further particularlypreferred aspects, the second feedstock comprises diesel, and the dieselcontains after hydrotreating and column separation less than 50 ppm,more preferably less than 25 ppm, and most preferably less than 10 ppmsulfur-containing products.

First and second hydrotreating reactors will preferably operate attemperatures that allow hydrotreating of the feedstock with a particularcatalyst without significant hydrocracking (i.e., with less than 15%conversion, and more preferably less than 10% conversion). Consequently,preferred temperatures will generally be in the range of about 500° F.to about 800° F., and more preferably between about 550° F. to about750° F. However, it should be recognized that depending on theparticular feedstock of the first and second reactors, the temperaturesmay vary accordingly. With respect to the temperature regulation in thesecond hydrotreater, it should be recognized that the temperature in thesecond hydrotreating reactor may also be regulated by the amount of thesecond feedstock that is fed into the second reactor. Moreover, itshould be recognized that the second hydrotreating reactor may beoperated to a relatively large extent through the heat and pressureprovided by the first hydrotreating reactor.

Similarly, the pressure of the first and second hydrotreating reactorsmay vary considerably, and a particular pressure will be at least inpart determined by the particular feedstocks and catalysts employed forthe hydrogenations. However, it is generally contemplated (a) theoperating pressure of the first hydrotreating reactor will be equal toor higher than the operating pressure of the second hydrotreatingreactor, and (b) that suitable pressures will generally be in the rangeof between about 1000 psi and 2400 psi. In further preferred aspects ofthe inventive subject matter, it is contemplated that the operatingpressure in the second reactor is between 0 and 300 psi less, and morepreferably between 0 and 150 psi less than the operating pressure in thefirst reactor.

Moreover, it should be recognized that by integration of twohydrotreating reactors into contemplated configurations, costs forconstruction and operation of contemplated plants will be significantlyreduced. For example, it is contemplated that the cost for a hydrogenrecycle compressor in contemplated configurations will be substantiallylower than the cost for two independent recycle compressors. In yetanother contemplated aspect, it is contemplated that the requiredcapacity increase for the heat exchanger and cooler within the recycleloop will be moderate to insignificant.

It should also be appreciated that suitable configurations may includeadditional hydrotreating reactors (i.e., a third reactor, a fourthreactor, etc.) and separators, wherein each of the additional reactorsare fluidly coupled to an existing or preceding reactor via a separatorthat receives the product of the existing or preceding reactor. Withrespect to the components (e.g., piping, hydrotreating reactor,compressor, heat exchanger, etc.) in contemplated configurations, it iscontemplated that all known and commercially available components may beemployed. Thus, contemplated configurations may be employed forproduction of two products having different boiling ranges and differentproduct specifications, wherein such configurations may be realized in anew plant as well as implemented as an upgrade to an existing plant Forexample, an existing gas oil hydrotreater upstream of a FCC unit may beupgraded to include a second reactor (or reactor section) for producinghigh quality low sulfur diesel fuel.

Consequently, a method of operating a plant may comprise a step in whicha first feedstock is hydrotreated in a first hydrotreating reactor toproduce a hydrotreated first feedstock. In another step, thehydrotreated first feedstock is fed into a hot separator that produces ahot hydrotreated liquid and a hot hydrotreated vapor that contains atleast a portion of the hydrotreated first feedstock. In a further step,at least a portion of the hot hydrotreated vapor is mixed with a secondfeedstock to form a mixed second feedstock, and in a still further step,the mixed second feedstock is fed into a second hydrotreating reactor toform a product, wherein the second feedstock has a boiling point rangethat is lower than the first feedstock. With respect to the first andsecond hydrotreating reactors, the hot separator, the feedstocks, andthe product, the same considerations as described above apply.

Thus, specific configurations and methods of combined hydrotreating havebeen disclosed. It should be apparent, however, to those skilled in theart that many more modifications besides those already described arepossible without departing from the inventive concepts herein. Theinventive subject matter, therefore, is not to be restricted except inthe spirit of the appended claims. Moreover, in interpreting both thespecification and the claims, all terms should be interpreted in thebroadest possible manner consistent with the context. In particular, theterms “comprises” and “comprising” should be interpreted as referring toelements, components, or steps in a non-exclusive manner, indicatingthat the referenced elements, components, or steps may be present, orutilized, or combined with other elements, components, or steps that arenot expressly referenced.

1. A system for integrated hydrotreating of a first and a secondfeedstock with different boiling point ranges, comprising: a firsthydrotreating reactor that receives a first feedstock and produces ahydrotreated first feedstock; a first hot separator configured toreceive the hydrotreated first feedstock and to produce a first hothydrotreated liquid and a hot hydrotreated vapor that contains at leasta portion of the hydrotreated first feedstock; wherein the firsthydrotreating reactor is configured such that the first hydrotreatedliquid has a conversion of less than 15% relative to the firstfeedstock; wherein the system is further configured such that at least aportion of the hot hydrotreated vapor is mixed with a second feedstockto form a mixed second feedstock; a second hydrotreating reactor that isconfigured to receive the mixed second feedstock and to form a product,wherein the second hydrotreating reactor is configured such that theproduct has a conversion of less than 15% relative to the mixed secondfeedstock; a second hot separator configured to receive the product andto form a liquid product; and wherein the second feedstock has a boilingpoint range that is lower than a boiling point range of the firstfeedstock.
 2. The system of claim 1 further comprising a first conduitconfigured to feed the first hydrotreated liquid to a firstfractionation zone, and a second conduit configured to feed the liquidproduct to a second fractionation zone.
 3. The system of claim 2 whereinthe hot separator is operated at a pressure of between about 1200 psiand about 2400 psi, and at a temperature of between about 450° F. and550°0 F.
 4. The system of claim 1 wherein the first hydrotreatingreactor operates at a first pressure and the second hydrotreatingreactor operates at a second pressure, and wherein the second pressureis between 0 and 300 psi less than the first pressure.
 5. The system ofclaim 4 wherein the first pressure is a pressure between about 1000 psiand 2400 psi.
 6. The system of claim 1 wherein the first feedstockcomprises gas oil.
 7. The system of claim 6 wherein the second feedstockcomprises diesel oil.
 8. The system of claim 7 wherein the firstfeedstock and the second feedstock have a ratio of between about 1:1 toabout 1:2.
 9. The system of claim 1 wherein the at least one of thefirst and second hydrotreating reactors further receive ahydrogen-containing stream.
 10. The system of claim 9 wherein at least aportion of the hydrogen-containing stream is recycled in the plant froman effluent of the second hydrotreating reactor.
 11. The system of claim9 wherein at least a portion of the hydrogen rich stream is a makeuphydrogen stream.
 12. The system of claim 1 wherein the hot separator andthe second hydrotreating reactor are integrated as an upgrade into anexisting hydrotreating plant.
 13. A method of hydrotreating comprising:hydrotreating a first feedstock in a first hydrotreating reactor toproduce a hydrotreated first feedstock at a conversion rate of less than15%; feeding the hydrotreated first feedstock into a hot separator thatproduces a hot hydrotreated liquid and a hot hydrotreated vapor thatcontains at least a portion of the hydrotreated first feedstock; mixingat least a portion of the hot hydrotreated vapor with a second feedstockto form a mixed second feedstock, and routing the hot hydrotreatedliquid to a first fractionation zone; feeding the mixed second feedstockinto a second hydrotreating reactor to form a product, feeding theproduct in a second hot separator to thereby form a product liquid, androuting the product liquid to a second fractionation zone; and whereinthe second feedstock has a boiling point range that is lower than aboiling point range of the first feedstock.
 14. The method of claim 13wherein the first feedstock comprises gas oil and wherein the secondfeedstock comprises diesel.
 15. The method of claim 13 wherein the hotseparator is operated at a temperature of between about 450° F. and 550°F. and a pressure of between about 1200 psi and about 2400 psi.
 16. Themethod of claim 15 wherein the first hydrotreating reactor operates at afirst pressure and the second hydrotreating reactor operates at a secondpressure, and wherein the second pressure is between 0 and 300 psi lessthan the first pressure.
 17. The method of claim 16 wherein the firstpressure is a pressure between about 1000 psi and 2400 psi.
 18. Themethod of claim 13 wherein the first feedstock and the second feedstockhave a ratio of between about 1:1 to about 1:2.
 19. The method of claim13 wherein the hot separator and the second hydrotreating reactor areintegrated as an upgrade into an existing hydrotreating plant.